Ceramic membranes can potentially provide increased value in applications that require robust performance in high temperature and highly corrosive environments. The ability to use a ceramic structure also would allow a process able to defoul or self-cleaning by simply back washing; this cannot be done with polymeric membranes. However, ceramic membranes are typically higher cost relative to polymer membranes, because they are expensive to manufacture in a large volume and maintain reasonable defect control. High volume, inexpensive processes such as extrusion of ceramic structures are inherently inaccurate at producing the controlled structures that are necessary for effective separations. The pore structure of a membrane determines the effective ability of it to filter the desired media or material. In order to work reliably these structures must have tight control or tolerances. The tolerances for defects for good quality gas separation membranes are extremely tight.
Unfortunately, ceramic membranes are prone to defects, including tiny pinholes, during the manufacturing operation. In general, the defect density tends to increase with higher processing speeds. Such defects are undesirable because they are non-selective, that is, they indiscriminately pass undesired components of a feed fluid, and they lower the selectivity of the membrane and result in diminished performance. Current high volume manufacturing processes involve high scrap rates due to the production of parts with high defect rates, and high temperatures associated with ceramic processing (sintering). The elimination of defects is essential to developing high performance composite films that can be economically produced at high speeds. The ability to effectively repair ceramic membranes with a low cost process would be a key enabler for the widespread use of ceramic membranes in a gas separations as well as water separation applications.